I used intel 4771 driver along with nvidia 381.xx series driver with following settings, do note I haven't changed the MS Hybrid settings because it was missing in that driver and only present when I updated to 388.xx & above.

Nvi reps and fellow members suggested those tweaks to Dan but in vain. He posted at Intel gpu driver forums and they said initial lab tested found the root cause and update will be shipped a little late. Dan requested a beta driver to test which I am yet to speculate if it fixes Optimus prime issues.